Rotating proprotor arrangement for a tiltrotor aircraft

Abstract

A propulsion system includes an engine disposed within a fuselage, a first gearbox coupled to the engine, a wing member having an upper wing skin and torque box formed by a first rib, a second rib, a first spar and second spar, a drive shaft coupled to the first gearbox and disposed within the wing member, a second gear box coupled to the drive shaft and disposed outboard from the second rib or inboard from the first rib, and a rotatable proprotor coupled to the second gear box. The rotatable proprotor includes a plurality of rotor blades, a rotor mast having a mast axis of rotation, and a proprotor gearbox coupled to the rotor mast. The proprotor gearbox is rotatable about a conversion axis, which intersects with the mast axis of rotation at a point within a central region of the torque box and above the upper wing skin.

What is claimed is: 
     
       1. A propulsion system for a tiltrotor aircraft having two rotatable proprotors, the propulsion system comprising:
 an engine disposed within a fuselage; 
 a wing member having a first rib, a second rib, a first spar, second spar and an upper wing skin, wherein the first rib, the second rib, the first spar and the second spar are coupled together to form a torque box proximate to each end of the wing member; 
 a first gearbox disposed midwing and coupled to the engine; 
 two second gear boxes, each second gear box for one of the rotatable proprotors and disposed either outboard from its respective second rib or inboard from its respective first rib; 
 two drive shafts disposed within the wing member, each drive shaft mechanically coupling the first gearbox to one of the second gear boxes; 
 each of the two rotatable proprotors mechanically coupled to one of the second gear boxes, each rotatable proprotor comprising:
 a plurality of rotor blades; 
 a rotor mast having a rotor mast axis of rotation; and 
 a proprotor gearbox coupled to the rotor mast, the proprotor gearbox being rotatable about a conversion axis, the conversion axis and the rotor mast axis of rotation intersecting at an intersection point, the intersection point being located in a central region within its respective torque box and above an airfoil surface profile of the upper wing skin. 
 
 
     
     
       2. The propulsion system as recited in  claim 1 , wherein the engine is disposed forward of the wing member, under the wing member or aft of the wing member. 
     
     
       3. The propulsion system as recited in  claim 1 , wherein the engine comprises two engines. 
     
     
       4. The propulsion system as recited in  claim 1 , further comprising an exhaust connected to the engine and extending to an upper portion of the fuselage aft of the wing member. 
     
     
       5. The propulsion system as recited in  claim 1 , further comprising an exhaust connected to the engine and extending to either side of the fuselage aft of the wing member. 
     
     
       6. The propulsion system as recited in  claim 1 , further comprising an inlet connected to the engine and blended into each side of the fuselage. 
     
     
       7. The propulsion system as recited in  claim 1 , further comprising an inlet connected to the engine and blended into a forward facing upper surface of the fuselage. 
     
     
       8. The propulsion system as recited in  claim 1 , wherein the conversion axis is parallel to a lengthwise axis of the wing member. 
     
     
       9. The propulsion system as recited in  claim 1 , further comprising:
 a direction change gearbox coupled to the engine; and 
 a riser shaft coupled to the direction change gearbox and the first gearbox. 
 
     
     
       10. The propulsion system as recited to  claim 1 , wherein the first gearbox comprises a single spiral bevel gear or a dual spiral bevel gear. 
     
     
       11. The propulsion system as recited in  claim 1 , wherein:
 the second gearbox comprises an interconnect gearbox; and 
 the proprotor gearbox comprises a single spiral bevel gear, or a quill shaft and a spindle gearbox. 
 
     
     
       12. The propulsion system as recited in  claim 1 , further comprising:
 an outboard housing; 
 an inboard housing; and 
 wherein an outboard portion of the proprotor gearbox is rotatably coupled to the outboard housing, and the inboard portion of the proprotor gearbox is rotatably coupled to the inboard housing. 
 
     
     
       13. The propulsion system as recited in  claim 12 , wherein the inboard housing and the outboard housing are structurally located above the upper wing skin of the wing member. 
     
     
       14. The propulsion system as recited in  claim 1 , wherein the tiltrotor aircraft comprises an unmanned aerial vehicle. 
     
     
       15. A tiltrotor aircraft, comprising:
 a fuselage; 
 an engine disposed within the fuselage; 
 a wing member having a first rib, a second rib, a first spar, second spar and an upper wing skin, wherein the first rib, the second rib, the first spar and the second spar are coupled together to form a torque box proximate to each end of the wing member; 
 a first gearbox disposed midwing and coupled to the engine; 
 two second gear boxes, each second gear box for one of the rotatable proprotors and disposed either outboard from its respective second rib or inboard from its respective first rib; 
 two drive shafts disposed within the wing member, each drive shaft mechanically coupling the first gearbox to one of the second gear boxes; 
 each of the two rotatable proprotors mechanically coupled to one of the second gear boxes, each rotatable proprotor comprising:
 a plurality of rotor blades; 
 a rotor mast having a rotor mast axis of rotation; and 
 a proprotor gearbox coupled to the rotor mast, the proprotor gearbox being rotatable about a conversion axis, the conversion axis and the rotor mast axis of rotation intersecting at an intersection point, the intersection point being located in a central region within its respective torque box and above an airfoil surface profile of the upper wing skin. 
 
 
     
     
       16. The tiltrotor aircraft as recited in  claim 15 , wherein the engine is disposed forward of the wing member, under the wing member or aft of the wing member. 
     
     
       17. The tiltrotor aircraft as recited in  claim 15 , wherein the engine comprises two engines. 
     
     
       18. The tiltrotor aircraft as recited in  claim 15 , further comprising an exhaust connected to the engine and extending to an upper portion of the fuselage aft of the wing member. 
     
     
       19. The tiltrotor aircraft as recited in  claim 15 , further comprising an exhaust connected to the engine and extending to either side of the fuselage aft of the wing member. 
     
     
       20. The tiltrotor aircraft as recited in  claim 15 , further comprising an inlet connected to the engine and blended into each side of the fuselage. 
     
     
       21. The tiltrotor aircraft as recited in  claim 15 , further comprising an inlet connected to the engine and blended into a forward facing upper surface of the fuselage. 
     
     
       22. The tiltrotor aircraft as recited in  claim 15 , wherein the conversion axis is parallel to a lengthwise axis of the wing member. 
     
     
       23. The tiltrotor aircraft as recited in  claim 15 , further comprising:
 a direction change gearbox coupled to the engine; and 
 a riser shaft coupled to the direction change gearbox and the first gearbox. 
 
     
     
       24. The tiltrotor aircraft as recited to  claim 15 , wherein the first gearbox comprises a single spiral bevel gear or a dual spiral bevel gear. 
     
     
       25. The tiltrotor aircraft as recited in  claim 15 , wherein:
 the second gearbox comprises an interconnect gearbox; and 
 the proprotor gearbox comprises a single spiral bevel gear, or a quill shaft and a spindle gearbox. 
 
     
     
       26. The tiltrotor aircraft as recited in  claim 15 , further comprising:
 an outboard housing; 
 an inboard housing; and 
 wherein an outboard portion of the proprotor gearbox is rotatably coupled to the outboard housing, and the inboard portion of the proprotor gearbox is rotatably coupled to the inboard housing. 
 
     
     
       27. The tiltrotor aircraft as recited in  claim 26 , wherein the inboard housing and the outboard housing are structurally located above the upper wing skin of the wing member. 
     
     
       28. The tiltrotor aircraft as recited in  claim 15 , further comprising a wing extension extending outboard from the rotatable proprotor. 
     
     
       29. The tiltrotor aircraft as recited in  claim 28 , wherein the wing extension includes a straight portion and an upwardly canted portion. 
     
     
       30. The tiltrotor aircraft as recited in  claim 28 , wherein the wing extension is rotatable or foldable. 
     
     
       31. The tiltrotor aircraft as recited in  claim 15 , wherein the tiltrotor aircraft comprises an unmanned aerial vehicle.